Vacuum circuit interruptor including a gettering device

ABSTRACT

A vacuum circuit interruptor having an improved gettering device. Stationary and movable contact members are positioned within a vacuum tight housing of the interruptor. A gettering device is also positioned within the housing for taking up any gases which may be released during the operation of the circuit interruptor and may be produced by leakage in order to maintain the desired vacuum. The gettering device includes the gettering substance which is heated by an electric current flow which is derived by a transformer action from the electric current flowing through the circuit interruptor.

United States Patent n91 Clason Mar. 18, 1975 VACUUM CIRCUIT INTERRUPTOR INCLUDING A GETTERING DEVICE [75] Inventor: Jan Christiaan Clason, Hengelo,

Netherlands [73] Assignee: I-Iazemeijer B.V., Hengelo,v

Netherlands [22] Filed: Oct. 17, 1973 21 Appl. No; 407,041

[30] Foreign Application Priority Data Oct. 18, 1972 Netherlands 7214103 [52] U.S. Cl 200/144 B [51] Int. Cl. H0lh 33/02 [58] Field of Search 200/144 B [56] References Cited UNITED STATES PATENTS 3,090,852 5/1963 Greenwood 200/144 B Primary E,ranziner-Harold Broome Attorney, Agent, or Firm-Watson, Cole, Grindle & Watson [57] ABSTRACT A vacuum circuit interruptor having an improved gettering device. Stationary and movable contact members are positioned within a vacuum tight housing of the interruptor. A gettering device is also positioned within the housing for taking up any gases which may be released during the operation of the circuit interruptor and may be produced by leakage in order to maintain the desired vacuum. The gettering device includes the gettering substance which is heated by an electric current flow which is derived by a transformer action from the electric current flowing through the circuit interruptor.

1 Claim, 2 Drawing Figures VACUUM CIRCUIT INTERRUPTOR INCLUDING A GETTERING DEVICE ary and movable contact members in vacuum in the housing, a gettering device in the housing for taking up any gases which may be released by the components of the circuit interruptor and may be introduced by leakage in order to maintain the desired vacuum. A similar apparatus is known.

For the proper operation of a vacuum circuit interruptor it is of essential importance, that the vacuum in the interrupting space is maintained. The vacuum is so high that the mean free path of the electrons is much longer than the spacing between the opened contact members. During the interrupting process of high electric currents the temperature of the contact members, the walls of the interrupting space and other components of the circuit interruptor will increase rapidly, and it is possible that the components will release some gas. After a number of interruptions the pressure in the interrupting space can become so high that the mean free path of the electrons has become equal to or smaller than the maximum contact spacing, so that the vacuum circuit interruptor can no longer function as a switch, i.e., can no longer switch off an electric current, since the space between the contact members has become electrically conductive.

In order now to take up the gases which have been released by-the various components of the vacuum circuit interruptor and may have entered through leakage, the vacuum circuit interruptor is provided with a gettering device. For-that purpose a so-called gettering substance is provided in the vacuum space, such as e.g., zirconium-aluminium or zirconium-titanium, which can absorb gas molecules. The gettering substance is in the form of a layer, for example, applied to the rod of one of the interrupting contact members. The absorptive power for gas molecules of the gettering substance increases as the temperature of the gettering substance rises. The taking up capacity of the gettering substance at room temperature is only and usually it is necessary to rise the temperature of the gettering substance to a value of about 400C. The gettering substance absorbs the gas molecules, which will thendiffuse into the bulk of the gettering substance vfrom the surface. The diffusing speed of the gas molecules into the gettering substance increases as the temperature of the gettering substance rises.

An objective of the invention is to bring the gettering substance in a vacuum circuit interruptor to a high temperature. For that purpose the gettering deviceis provided with a gettering substance which is heated by an electric current flow which is derived by transformer action from the electric current, flowing through the circuit interruptor.

In an embodiment of the invention, the gettering device includes an annular iron core arranged about the rod of the stationary contact member. A plurality of metal sheets are arranged around the annular core, which sheets act as the secondary winding and also as the secondary load ofa transformer. The rod acts as the primary winding of the transformer. The gettering substance is deposited as a layer on the metal sheets.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now further be explained in reference to a specific embodiment illustrated in the annexed drawing, in which:

FIG. 1 is a longitudinal cross section of the vacuum circuit interruptor according to the invention, and

FIG. 2 is a cross sectionalong line II-II through the gettering device of the vacuum circuit interruptor according to FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vacuum circuit interruptor according to the invention includes a metal housing 1, usually of cilindrical form, to which in vacuum tight fashion two insulators, 2, 3 are secured. The contact rod 4- of the stationary contact member 5 is passed through the one insulator 3, and the contact rod 4 is secured to the insulator 3 by the rings 6 in a vacuum tight fashion. The movable contact, which in the left hand portion of FIG. 1 is illustrated in a partially sectional view and in the right hand portion of FIG. 1 in its closed view, is constituted by the contact member 7 and the contact rod 8, which is secured to one end of a metal bellows 9. The other end of bellows 9 is secured in vacuum tight fashion in the other insulator 2 by means of the rings 20. Thus the movable contact member 7 can be opened and closed, with which the bellows 9 is compressed and extended, respectively, without the vacuum in the interrupting space 10 being disturbed. The contact rod 8 of the movable contactmember 7 is provided at 11 with a screw connected operating rod, which is not illustrated. In the interrupting space 10, screening rings 12, 13 are disposed to prevent copper vapours which are released by the copper contact members 5, 7 during the interrupting process from depositing on the internal cylindrical surface of the insulators 2, 3 which otherwise would be bridged so that the interruptor would be shorted.

At the lower end of the vacuum circuit interruptor a pumping stem 14 is illustrated, with which the circuit interruptor is evacuated in the factory, but which is sealed vacuum tight on the finished interruptor.

Around a portion 15 of the contact rod 4 of the stationary contact member 5, the gettering device according to the invention is arranged. The gettering device includes a soft iron ring'core 16, around which a large number of metal sheets 17 is disposed, a layer of a gettering substance being applied to the sheets 17. The crown of metal sheets 17 rests on a collar 18 of the contact rod 5, while the sheets 17 with their other ends bear against a ring 19, which is connected to the contact rod 4. Thus the gettering device cannot move in the axial direction with respect to the contact rod 4. If the vacuum circuit interruptor is closed, as illustrated in the right hand portion of FIG. 1, the contact rod. 4 of the stationary contact member 5 functions as the current flow primary winding of a transformer, while the metal sheets 17 act as the secondary winding and also as the secondary load, the ring core 16 constituting the iron magnetic circuit. The metal sheets 17 are sufficiently heated by the secondary-current flowing therein to bring the gettering substance on the sheets to the operating temperature. As explained above the operating temperature should be about 400C. With that temperature the diffusion speed of the gas molecules into the to maintain the desired vacuum,.said gettering device including an annular iron core arranged about said stationary rod;

transformer means having as its primary winding, said stationary rod and as its secondary winding, a plurality of metal sheets arranged around said annular iron core and transferring an electric current flow from the current interruptor through said primary winding to said secondary windings; and

gettering material being deposited as layers on said metal sheets so as to be heated by the electric current through said metal sheets, which act as said secondary windings. 

1. A vacuum circuit interruptor comprising: a vacuum tight housing; a stationary rod; stationary and movable contact members positioned within said vacuum tight housing, said stationary contact member being mounted on said stationary rod; a gettering device arranGed within said vacuum tight housing for absorbing any gases which may be released during operation of the circuit interruptor and may be introduced through leakage, in order to maintain the desired vacuum, said gettering device including an annular iron core arranged about said stationary rod; transformer means having as its primary winding, said stationary rod and as its secondary winding, a plurality of metal sheets arranged around said annular iron core and transferring an electric current flow from the current interruptor through said primary winding to said secondary windings; and gettering material being deposited as layers on said metal sheets so as to be heated by the electric current through said metal sheets, which act as said secondary windings. 